Electron Spin Resonance in Quasi-One-Dimensional Quantum Antiferromagnets: Relevance of Weak Interchain Interactions

TL;DR

This paper investigates how weak interchain interactions influence electron spin resonance linewidths in quasi-one-dimensional antiferromagnets, revealing temperature-dependent broadening effects and explaining experimental observations in specific compounds.

Contribution

It introduces a theoretical framework linking interchain anisotropic interactions to ESR linewidth broadening in weakly coupled spin chains, explaining experimental anomalies.

Findings

ESR linewidth increases as temperature decreases in coupled chains.

Single chains show linewidth proportional to temperature.

Theory explains experimental linewidth broadening in specific compounds.

Abstract

We discuss universal features on the electron spin resonance (ESR) of a temperature-induced Tomonaga-Luttinger liquid phase in a wide class of weakly coupled $S=1/2$ antiferromagnetic spin chains such as spin ladders, spin tubes and three-dimensionally coupled spin chains. We show that the ESR linewidth of various coupled chains increases with lowering temperature while the linewidth of a single spin chain is typically proportional to temperature. This broadening with lowering temperature is attributed to anisotropic interchain interactions and has been indeed observed in several kinds of three-dimensional (3D) magnets of weakly coupled spin chains above the 3D ordering temperature. We demonstrate that our theory can account for anomalous behaviors of the linewidths in an $S=1/2$ four-leg spin tube compound Cu$_2$Cl$_4 \cdot $H$_8$C$_4$SO$_2$ (abbreviated to Sul-Cu$_2$Cl$_4$) and a three-dimensionally coupled $S=1/2$ spin chain compound CuCl$_2\cdot 2$NC$_5$H$_5$.